The National Weather Service issued a succession of Flash Flood Warnings for Chicago and its southern and western suburbs Tuesday after overnight thunderstorms soaked the region and a second, more intense band of storms moved in during the afternoon. The warnings, covering much of Cook, central Will and southeastern DuPage counties, run through 8 p.m. CDT, while a broader Flood Watch remains in effect until midnight. Forecasters said Doppler radar and automated gauges were detecting rainfall rates of two to three inches an hour, on top of more than an inch that fell earlier in the day. Atmospheric conditions, they added, could support localized totals high enough to swamp viaducts and low-lying roads. The agency urged motorists to avoid flooded streets and residents to monitor rapidly changing conditions. The severe weather has already disrupted transportation and power supplies. The Federal Aviation Administration imposed ground stops at Midway International Airport until 5:15 p.m. and at O’Hare International Airport until 5:45 p.m., citing lightning and low visibility. Utility ComEd reported several thousand customers without electricity across Chicago and the south suburbs by mid-afternoon. While the brunt of the storm system is centered on the Chicago metropolitan area, special weather statements and severe-thunderstorm alerts were also posted from central Minnesota through northwestern Indiana and as far west as northern Nevada and Arizona. Meteorologists expect the line of storms to clear the Chicago region later Tuesday evening as a cold front sweeps across the Great Lakes.